Babies who experience forceps-aided births are more likely to develop a more pronounced response to stress, researchers have found.

A team from Queen Charlotte's and Chelsea Hospital, London, found that infants' response to stress at eight weeks of age may be closely related to the way they were delivered during childbirth.

The researchers monitored infants' response to the mild pain of a routine inoculation given while they were seated on their mother's lap.

They noted how much they cried, and measured the level of the stress hormone cortisol in their saliva.

Infants born by assisted delivery with the aid of forceps were found to have the greatest stress response.

The lowest stress response was exhibited by infants born by Caesarean section.

Infants born by natural delivery without assistance showed an intermediary stress response compared to the other two types of childbirth.

Difficult to soothe

The study, published in The Lancet, supports the widely held but anecdotal view that babies born by assisted delivery are difficult to soothe.

The researchers also argue that if a mother is stressed by a difficult birth, she may influence the way her child responds to stressful situations.

The study follows previous research that has established a link between an early experience of pain, such as circumcision after birth, and a more pronounced reaction to pain.

Previous research has also found evidence of a link between pregnancy and childbirth complications and the later development of schizophrenia in males.

A Canadian study published in 1998 found that children born by Caesarean section could be more likely to develop schizophrenia.